PE 3070 Week 4 Notes
PE 3070 Week 4 Notes PE 3070
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This 6 page Class Notes was uploaded by Aurora Moberly on Saturday September 17, 2016. The Class Notes belongs to PE 3070 at Southern Utah University taught by Dr. Julie Taylor in Fall 2016. Since its upload, it has received 6 views. For similar materials see Exercise Physiology in Physical Education at Southern Utah University.
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Date Created: 09/17/16
Test: 10/5 PE 3070 Most commonly missed questions from exam 1: 1. Which of the following is not part of a muscle fiber? 2. The all or none principle indicates that when threshold is exceeded the muscle fibers will? 3. What event causes the myosin cross bridges to release from the actin? 4. Which is the primary factor for determining muscle contraction speed? 5. Which of the following is not true regarding fast twitch and slow twitch fibers? Chapter 2: Bioenergetics and Muscle Metabolism Substrates: Fuel sources from which we make energy molecules (ATP): CHO, fat, protein Bioenergetics: Process of converting substrates into energy; Performed at a cellular level Metabolism: Chemical reactions in the body Catabolism: Breaks things down Anabolism: Building things ATP: Only 40% of total energy consumed is used to generate ATP, 60% is released as heat ATP is a highenergy compound the primary energy molecule for the human body, derived from food sources and local phosphorylation When the ATP molecule combines with water and ATPase the last phosphate group splits away releasing large amounts of free energy reducing ATP to ADP and P i Phosphorylation: A phosphate group is added to the lowenergy compound, ADP, to form ATP Substrate Level Phosphorylation: ATP generated independent of oxygen Oxidative Phosphorylation: ATP generation that requires oxygen Energy: 1 kilocalorie is the amount of heat energy needed to raise 1L of water 1°C CHO and Protein 4kcal/g; Fat 9kcal/g CHO: CHO is the preferred substrate because it is an easier molecule to metabolize and is used in 2 out of 3 energy pathways CHO is found in the body as blood glucose, liver glycogen, muscle glycogen Fat: Fat is less readily available because it has to be reduced from triglycerides to glycerol and free fatty acids Free fatty acids (FFA) are used to form ATP Protein: Only used for energy during very long bouts of exercise or starvation Gluconeogenesis: The process by which protein is converted into glucose Lipogenesis: The process of converting protein into FFA Only the amino acids of protein can be used for energy Rate of Energy Production Rate is determined by 1. Availability of the primary substrate 2. Enzyme activity 3. Cofactors Mass Action Effect: Increased substrate availability increases the rate of the metabolism Enzymes: Proteins that speed up reactions by lowering the activation energy required to begin a reaction Many enzymes require cofactors to function so their availability can effect enzyme activity as well RateLimiting Enzyme: One enzyme that controls the rate of the reaction The three energy systems are (in order of speed): 1. Phosphagen System (Anaerobic metabolism) 2. Glycolysis (Anaerobic metabolism) 3. Oxidative Phosphorylation (Aerobic metabolism) All three systems are always active Phosphagen System: ATPPCr System and Myokinase System Initiates every muscular movement; Substrate level metabolism; CHO only Phosphocreatine (PCr): Another highenergy molecule stored in cells Local Phosphorylation: ATP production that occurs within the muscle cell This system can sustain the muscles energy needs for 315sec during high intensity exercise ATPPCr System: ATPPCr is used more than myokinase system PCr + ADP + Creatine kinase ATP + Creatine The energy released from the break of PCr is used to regenerate ATP Creatine Kinase: Enzyme that breaks P from Pir Activity is increased when concentrations of ADP or P are iicreased Activity is inhibited when concentrations of ATP are increased Myokinase System: Not the preferred pathway because we don't have a lot of myokinase 2ADP + Myokinase ATP + AMP Glycolytic System: 1. Glycolysis begins with a 6carbon glucose molecule (glucose6phosphate) Two sources of 6carbon glucose are blood glucose and muscle glycogen Blood glucose is converted to glucose6phosphate by the enzyme hexokinase, this process costs one ATP Muscle glycogen is converted to glucose6phosphate by the enzyme phosphorylase, this doesn't cost any ATP 2. Phosphofructokinase (PFK): Rate limiting enzyme for glycolysis, used early in the glycolysis process Uses one ATP If ATP concentrations are high the activity of PFK decreases If ADP and P concentrations are high the activity of PFK increases i 3. Fast Glycolysis: Glycolysis done in the absence of oxygen + Produces 2 H that are transported to the electron transport chain (ETC) by coenzyme NAD 4. Aerobic Glycolysis: Glycolysis done in the presence of oxygen + Produces 2 H that are transported to the ETC by coenzyme NAD 5. Pyruvate: End product of glycolysis Fast glycolysis produces pyruvate that is converted to lactic acid which then dissociates into lactate and a free hydrogen; Lactate then goes into the Cori Cycle Aerobic glycolysis produces pyruvate that is converted with the help of oxygen to acetyl CoA that then travels to the mitochondria to begin oxidative phosphorylation 6. Products of Glycolysis: Blood glucose glycolysis results in a net production of 2 ATP Muscle glycogen glycolysis results in a net production of 3 ATP Glycolysis results in 4 H ions (2 from fast glycolysis and 2 from aerobic glycolysis) Glycolysis results in 2 pyruvate molecules that can be converted to lactic acid or acetyl CoA Fatigue from glycolysis occurs because of the buildup of H causing acidification of muscle fibers which impairs glycolytic enzyme function; Acid also decreases muscle fibers calciumbinding capacity impeding muscle contraction Glycolysis operates within the cell cytoplasm Glycolysis used during the first 2 minutes of highintensity exercise Substrate can only be carbohydrates Cori Cycle: How the body processes lactic acid/lactate Lactate in the muscle diffuses into the blood stream then travels to the liver Lactate in the liver goes through a series of enzymatic (cori cycle) steps and is converted to glucose that can reenter the blood stream or it is converted to glycogen and stored in the liver Oxidative System (Overview): Occurs in the mitochondria Substrates can be carbohydrates or fats All of the CO2 we breath out comes from this process Three main processes: Glycolysis, Krebs cycle, Electron transport chain 1. Pyruvic acid from glycolysis is converted to acetyl CoA 2. Acetyl CoA enters the Krebs cycle and forms ATP, carbon dioxide and hydrogen 3. Hydrogen in the cell combines with two coenzymes NAD and FAD that carry it to the ETC 5. ETC Hydrogen gradient produces ATP 7. ETC recombines hydrogen atoms with oxygen to produce water and prevent acidification of the muscle 8. ATP production results in 32/33 from glucose/glycogen or 100+ from FFA 9. Products: ATP, CO , 2ater Oxidative System: Krebs Cycle Glucose produces two pyruvates therefore two acetyl CoA are formed and two complete Krebs cycles occur Products (1 Krebs cycle):4 (3NAD 1FAD), 6 CO2, 1 ATP Oxidative System: Electron Transport Chain Electron Transport Chain: A group of mitochondrial protein complexes located in the inner mitochondrial membrane H are transported to the ETC via NAD and FAD + + Every H that NAD drops off to the ETC results in 3 ATP but nets 2.5 ATP because it costs energy to transport H Every H that FAD drops off results in a net of 1.5 ATP H are pumped out of the mitochondrial matrix and as they move back across the membrane down their concentration gradient energy is transferred to ADP and ATP is formed At the end of the chain H combines with oxygen to form water preventing acidification of the cell Net energy production is 33/34 ATP per molecule of glucose/glycogen Oxidative System: Fat Fat is stored as triglyceride and broken down into one molecule of glycerol and three molecules of FFA this process is known as lipolysis Lipases: Enzymes that break down triglycerides; Occurs in the fat cell Fat is stored within muscle fibers and in adipose tissue cells called adipocytes βoxidation: Process in which FFAs are converted into acetyl CoA; Requires 2 ATP for activation Every two carbons is broken off to form acetyl CoA so if you have a 16carbon FFA it will form 8 acetyl CoA + Every bond broken in FFA releases 2 H (1NAD 1FAD) that are shuttled over to the ETC FFA requires more oxygen because FFA contains more carbon molecules than a glucose molecule Fats are heterogeneous and the amount of ATP produced depends on the specific fat oxidized Oxidative System: Protein Gluconeogenesis: Process of glucose being converted amino acids When amino acids are catabolized they release nitrogen; Nitrogen cannot be oxidized by the body Nitrogen can be used to form new amino acids or is converted to urea and excreted out of the body through urine This conversion requires the use of ATP Oxidative Capacity of Muscle: Oxidative Capacity of Muscle: The maximal capacity of muscle to use oxygen Depends on three things 1. Oxidative enzyme concentrations 2. Fiber type composition 3. Oxygen availability Enzyme activity can be measured to determine the oxidative capacity of a muscle The most commonly measured enzymes are succinate dehydrogenase and citrate synthase The more oxidative enzyme activity a muscle has the greater its oxidative capacity Type I fibers have a greater capacity for aerobic activity because they have more mitochondria at greater concentrations than type II fibers The more type I fibers a muscle has the greater its oxidative capacity Type II fibers can be trained to have a greater oxidative capacity In response to exercise the body increases respiration, heart rate, force of heart beat, dilates arterioles, ect. this is all done to increase oxygen levels in the body The availability of oxygen is the number one determinate of the oxidative capacity of a muscle The human body stores little oxygen so the oxygen entering the blood is directly proportional to the amount of oxygen used by tissues for oxidative metabolism Enzymes Overview: Creatine Kinase: Breaks apart PCr to form ATP in the phosphagen system Myokinase: Breaks apart one ADP to form ATP from another ADP in the phosphagen system Hexokinase: Breaks apart one ATP to form glucose6phosphate from blood glucose to begin glycolysis Phosphorylase: Converts muscle glycogen to glucose6phosphate to begin glycolysis Phosphofructokinase (PFK): Rate limiting enzyme of glycolysis; Uses one ATP to convert molecules early in the glycolysis process Myosin ATPase Succinate Dehydrogenase Citrate Synthase Consider FAST Glycolysis 1. How many total ATP are generated from complete catabolism of a 6C glucose molecule? How many ATP are required (cost) to metabolize a 6C glucose molecule? What is the NET yield of ATP for a glucose molecule? 2. How many total ATP are generated from complete catabolism of a 6C glycogen molecule? How many ATP are required (cost) to metabolize a 6C glycogen molecule? What is the NET yield of ATP for a glycogen molecule? 3. How many H+ ions are released during the conversion of CHO to 2 pyruvate molecules? These H+ ions are transported to the mitochondria/ETC by what coenzyme? 4. How many H+ ions are released during the conversion of 2 pyruvate molecules to acetyl CoA? These H+ ions are transported to the mitochondria/ETC by what coenzyme? 1 2 3 4 5 6 7 8 9 10 12 11 ↓ ↓ ↓ 14 13 15
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